1. Technical Field
This invention relates to a vehicle notification system and, more particularly, to a vehicle notification system for automatically warning a driver of potential dangers while driving.
2. Prior Art
Various systems have been proposed to inform motorists of traffic hazards. Some systems use modulated carrier signals to convey traffic information. Unfortunately, many modern vehicle passenger compartments are designed and built to be quiet when their windows are closed. Outside noises coming from car horns and radios are prevented from entering the passenger compartment and distracting the driver. Unfortunately, emergency vehicle sirens and train whistles are also prevented from entering the passenger compartment. Car radios or sound systems played at moderate levels inside the vehicle make it even more difficult to hear outside alarms. Thus, an emergency vehicle siren or a train whistle may be undetected by the occupants of a vehicle. This creates a hazardous situation on the highways.
Emergency vehicles need an unobstructed path to respond to an emergency within an acceptable time frame. The occupants of the emergency vehicle need to be able to change traffic signals and alert the drivers of other vehicles to the presence of the emergency vehicle. In the past, radio frequency energy has been used to alert the occupants of one vehicle to the presence of another vehicle. Radio frequency signals were transmitted from one vehicle and detected by an unsuspecting second vehicle. Upon detection, a warning signal was generated in the second vehicle.
In a rural area, where few emergencies occur and few trains travel, an occasional interruption by a train or emergency vehicle alarm signal may be acceptable. However, in a city or suburban environment, emergencies occur more frequently. Constant interruption of the radio and subsequent distraction of the driver due to an emergency occurring many blocks away may create a hazard. Thus, a signal limited in range by objects in its path is desired. It is also desirable to change traffic signals in the immediate vicinity of the emergency vehicle.
To be useful in cities and suburbs, the energy transmitted by the emergency vehicle's alarm system must be limited to the immediate vicinity. The system should regulate traffic flow by changing traffic signals and alerting the drivers of vehicles to the presence of an emergency vehicle.